The term versioning is applied to the creation and management of multiple releases of an object such as a document, where all releases have the same general features but are improved, upgraded or customized. Commonly, the term is used for digital documents such as application source codes, operating systems, software packages, and management of data, art resources such as blueprints or electronic models, and other projects.
Data versioning is performed for a number of purposes including increased concurrency for applications requiring concurrency control, providing snapshot isolation for consistent data reads, and for the creation of backup snapshots to help recovery from hardware and software errors. Versioning involves retaining pre-update data values after data have been updated. For example, in case an error occurs and the results of a calculation are incorrect, restoring the pre-update data values could be very helpful. Versioning can be done incrementally on every update of each document (i.e., transactional versioning) or done globally at certain times (i.e., check-pointing with snapshots).
Using version control, one can keep track of different versions of electronic information, for example, in collaborative data sharing and editing among users of systems that employ different versions of a document. Version control systems are typically stand-alone applications. With the spread of use of non-volatile memories such as flash memories, there is a need for techniques that enable transactional versioning at the data element level, versioning for global snapshots, and other methods of version control in flash memories.